Step 1: Understanding the Question:
The velocity of the particle is given as a function of position:
\[
v = x^2 - 5x + 4
\]
We are asked to find the magnitude of acceleration when the velocity becomes zero.
Step 2: Key Formula or Approach:
Acceleration can be written as:
\[
a = \frac{dv}{dt} = \frac{dv}{dx} \cdot \frac{dx}{dt} = v \frac{dv}{dx}
\]
Step 3: Detailed Explanation:
First, find when velocity is zero:
\[
x^2 - 5x + 4 = 0
\]
\[
(x - 1)(x - 4) = 0
\Rightarrow x = 1 \text{ or } x = 4
\]
Now, compute:
\[
\frac{dv}{dx} = 2x - 5
\]
Acceleration:
\[
a = v \cdot (2x - 5)
\]
At both \( x = 1 \) and \( x = 4 \), we already know:
\[
v = 0
\]
So,
\[
a = 0 \cdot (2x - 5) = 0
\]
Step 4: Final Answer:
The magnitude of acceleration is:
\[
\boxed{0}
\]